The present invention is drawn to a method of manufacturing double walled vessels having control or other apparatus extending through the outer vessel and into the inner vessel. More specifically, the present invention is drawn to a novel method of manufacturing water heaters comprising inner and outer shells.
Most water heaters in use today are comprised of double walled vessels having an inner shell designed to contain heated water and an outer shell arranged over and around the inner shell to protect and support the inner shell. The outer shell also serves to retain a layer of insulation around the inner shell and is a mounting point for various controls used to operate and monitor the water heater. Typically, both the inner and outer shells of a water heater are fabricated from steel. However, water heaters fabricated from steel are subject to corrosion and impact damage that may adversely affect the appearance of the water heater and even render it inoperable. Furthermore, failure in a steel water heater often results in the escape of the water contained within the inner shell of the water heater thereby causing unacceptable water damage to the structure where the water heater is installed.
Standard metallic water heaters typically utilize spun fiberglass type insulation between the inner and outer shells of the vessel in order to insulate the inner shell and render the operation of the water heater more efficient. Should condensation on the pipes connecting the water heater to a water system of a structure, or a leak in those pipes, cause the fiberglass insulation to become wet, the efficiency of the water heater is greatly reduced. In addition, damp insulation may also become an incubator for organisms such as fungi or bacteria, which may cause the water heater in question to give off an unpleasant odor.
Another drawback to the use of standard metallic water heaters is that the fabrication of the water heater itself is relatively labor and material intensive. What is more, the equipment required to manufacture a metallic double walled vessel such as the standard metallic water heater described above is costly and takes up a large amount of space on a factory floor.
Therefore, it can be seen that it would be beneficial to provide a water heater which is rust proof, highly resistant to impact forces, and which is well insulated within insulation resistant to damage caused by dampness. Furthermore, it would be very beneficial to provide a method for rapidly and efficiently fabricating and assembling such a water heater.